I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[12163]
Open Access
Abstract: High energy X-ray diffraction (HEXRD) was used to characterize the amorphous structure of the as-prepared binary Ca61Al39 (at.%) metallic glass and its evolution during thermal loading. The investigation was performed in both reciprocal and real space by means of the first diffuse peak (FDP) analysis and the reduced atomic pair distribution function (PDF) analysis, respectively. It was found that bond lengths of the atomic CaeCa and CaeAl pairs of the as-prepared structure were 3.70 Å and 3.24 Å, respectively.
The coordination number of the first coordination shell was estimated to be 11.9. The analysis of the FDP
behaviour during thermal treatment proposed the existence of the elaxation temperature Tr at 150 °C.
Analysis of summations of all absolute differences between two consecutive intensity curves in the region of the FDP as a function of temperature revealed two crystallization temperatures at 280 °C and
305 °C. Products of a devitrification process were identified to be alike a triclinic Ca8Al13 and monoclinic
Ca13Al14 phase.
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Dec 2016
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I15-Extreme Conditions
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D. M.
Fronczek
,
K.
Saksl
,
R.
Chulist
,
S.
Michalik
,
J.
Wojewoda-Budka
,
L.
Sniezek
,
M.
Wachowski
,
J.
Torzewski
,
M.
Sulikova
,
K.
Sulova
,
A.
Lachova
,
M.
Fejercak
,
D.
Daisenberger
,
Z.
Szulc
,
Z.
Kania
Diamond Proposal Number(s):
[18639]
Abstract: Synchrotron radiation and XRD2 method were used to investigate the residual stress distribution before and after three point bending tests within an explosively welded composite composed of two light metals, namely: Ti gr. 2 and A1050. The analysis has shown that the bimetal is slightly affected by the explosive welding process since negative sign values of stress tensor were detected only in the immediate vicinity of interface of Ti gr. 2 characterized by a width of about 0.25 mm. Upon bending higher negative compression stresses are detected in this area as the σ11 value changes from −500 MPa to −1200 MPa. Additionally, the analysis of microstructure has revealed significant changes in twins morphology with primary and conjugate twinning before and after bending, respectively. However, the compressive twinning was the dominant system in both cases. Bending has changed the initial bimodal texture developing more spread basal components towards the transverse direction. The sample surface has been also significantly affected as the presence of compressive residual stress (−500 MPa) after bending was measured.
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Oct 2018
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K.
Saksl
,
Z.
Molčanová
,
J.
Durisin
,
S.
Michalik
,
L.
Temleitner
,
B.
Balloková
,
V.
Girman
,
Y.
Katuna
,
M.
Sulikova
,
K.
Sulova
,
M.
Fejercak
,
M.
Lisnichuk
,
A.
Lachová
,
L.
Kapuscinský
Abstract: Very low density eutectic Ca72Mg28 at.% alloy is a precursor of complex biodegradable alloys with potential use as bioresorbable alloy for orthopaedic applications. The structure of the amorphous alloy was investigated by using X-ray, neutron diffraction and reverse Monte Carlo (RMC) modelling. The RMC configuration was decomposed into polyhedral holes whose faces are all triangles consisting of chemical bonds. Free volumes in the respective polyhedral holes were evaluated with reference to the packing efficiency of crystalline CaMg2 HCP phase. The tetrahedral holes, accounting for about 55% of the whole space, are regarded as densely packed units because the average packing efficiency of them is approximately equal to that of the corresponding crystal phase. At the same time, various types of polyhedral holes which have a certain free volume have been observed, and some of them are connected with each other. The densely packed coordination polyhedra consisting only of tetrahedral holes tend to be clustered.
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Jun 2019
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I15-1-X-ray Pair Distribution Function (XPDF)
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Zuzana
Molčanová
,
Beáta
Balloková
,
Juraj
Durisin
,
Katarina
Sulova
,
Michaela
Sulikova
,
Andrea
Lachova
,
Maksym
Lisnichuk
,
Milos
Fejercak
,
Slávka
Martinková
,
Stefan
Michalik
,
Karel
Saksl
Diamond Proposal Number(s):
[20770]
Open Access
Abstract: In surgery, besides the joint replacements that need permanent prosthesis implantation in the human body, there are many other clinical cases, such as bone fracture, cardiovascular diseases, in which the temporary implant materials are needed. The fixation or mechanical support are there temporarily needed during the healing process of the injured or pathological tissue, and after that, the implants accomplish their mission have no longer function in human body. In this case, biodegradable materials are the optimal choice as these materials do their job while healing and a new tissue forming occur and degrade in the human body thereafter. Amorphous alloys based on magnesium and calcium are nowadays a very perspective group of metallic glasses. We have developed composition series of completely new (not published) ternary Ca-Mg-Au biodegradable alloys with attractive properties in terms of possible future applications (density and elastic modulus comparable to human bones, wide supercooled liquid region etc.). Although the rate of their degradation in physiological solutions is still too fast, these ternary alloys will serve as precursors for design of future highly alloyed systems with tuned dissociation rate in human body.
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Nov 2019
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I15-Extreme Conditions
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Diamond Proposal Number(s):
[18273]
Abstract: Attaining robust magnetic long-range order in ferroelectric Aurivillius-phase oxides at room temperature has recently attracted considerable attention of material scientists and engineers for the development of magnetoelectric-active materials in microelectronics and spintronics. Here, we report the structural evolution and its relation to the macroscopic magnetization of the series samples of Aurivillius (Bi4.3Gd0.7)(Fe1-xCox)1+yTi3-2yNbyO15 (x=0, 0.3, 0.5 and y=0, 0.3) compounds prepared by solid state reaction, aiming at shedding light on the Co substitution-induced ferromagnetism at room temperature and above. The Co-free composition showed a single-phase four-layered Aurivillius structure (a space group A21am), while the Co substitution was found to give rise to a mixed-layer structure composed of four- and three-layered phases. Rietveld analysis of the synchrotron X-ray diffraction data showed that the reduction in the number of layers across the Aurivillius morphotropic transition boundary is accompanied by a structural phase transformation from A21am to B2cb. The disordered intergrowth of these phases was evidenced by high-resolution transmission electron microscopy and found to originate from a nanoscale structural modulation occurring at the interface between the two phases. A sextet suggesting a long-range magnetic ordering in the doped samples was deduced from Mössbauer spectra. Magnetic-property measurements, indeed, confirmed a ferromagnetic state of these samples at elevated temperatures. The highest values of the remanent and saturation magnetization at room temperature were obtained for the compositions with x=0.3, in which the occurrence and enhancement of the magnetization can be attributed to the ferromagnetic clustering of the FeO6 and CoO6 octahedra and, partly, also to the spin canting effects and/or a double-exchange magnetic interaction between the mixed valence cobalt through oxygen. The cooperative freezing of randomly distributed Fe-O-Co clusters is suggested to be responsible for the spin glass-like behaviour observed at low temperatures.
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May 2020
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I15-1-X-ray Pair Distribution Function (XPDF)
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M.
Lisnichuk
,
Y.
Katuna
,
K.
Saksl
,
M.
Fejercak
,
M.
Sulikova
,
S.
Michalik
,
E.
Čižmár
,
A.
Kliuikov
,
V.
Girman
,
S.
Vorobiov
,
Z.
Molčanová
,
B.
Balloková
,
P.
Sovák
Diamond Proposal Number(s):
[20770]
Abstract: Solid phase stability and magneto-caloric effect of a ternary Gd50Co48Fe2 amorphous as-spun ribbons was studied in this work. The magnetization curve was measured at temperature range from 200 to 360 K. Subsequently the isothermal magnetization curves were measured as well at temperatures ranging from 200 to 350 K and at magnetic field between 1 to 5 T, using SQUID. Based on these experimental data, the magnetic entropy changes were determined. Thermal stability and phase composition of amorphous alloy was experimentally confirmed by difference scanning calorimetry and synchrotron X-ray diffraction. At elevated temperatures two crystallization events were observed. It has been found that the investigated alloy is a prospective aspirant for magnetic cooling devices.
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May 2020
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[14465, 16332]
Abstract: Detailed information on the atomic arrangement of glassy Cu54Hf46, Cu61Hf39 and Cu69Hf31 alloys has been obtained by the reverse Monte Carlo (RMC) simulation using high-energy X-ray diffraction and neutron diffraction data as input. Dominant cluster units are identified by means of the radical Voronoï tessellation technique. Cu-centred clusters show a stronger ordering level than the Hf-centred ones. Results are compared with those previously reported for analogous binary amorphous systems such as Zr–Cu and Zr–Ni. Additionally, the thermal stability of the studied Cu–Hf alloys has been inspected by in-situ high-temperature X-ray diffraction and differential scanning calorimetry measurements. A different structural evolution is observed for Cu69Hf31 compared with Cu54Hf46 and Cu61Hf39. Products of devitrification are identified and quantified. The better glass forming ability of Cu54Hf46 and Cu61Hf39 compared with Cu69Hf31 is explained in the view of short range order differences of glassy states and corresponding crystalline phases formed during devitrification.
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Aug 2020
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Michaela
Sulikova
,
Zuzana
Molčanová
,
Beata
Ballóková
,
Juraj
Durisin
,
Slávka
Martinková
,
Dagmara
Varcholová
,
Stefan
Michalik
,
Robert Tang
Kong
,
Logan
Ward
,
Apurva
Mehta
,
Katarína
Sulova
,
Miloš
Fejercak
,
Andrea
Lachova
,
Róbert
Džunda
,
Karel
Saksl
Abstract: In surgery, in addition to joint replacement, which requires permanent implantation of the prosthesis into the human body, there are many other clinical cases where fixation or mechanical support are only temporarily needed during the healing process of the injured or pathological tissue. In this case, biodegradable materials are the optimal choice as these materials do their job and degrade in the human body thereafter. Amorphous magnesium-zinc based alloys are nowadays a very promising group of metallic glasses (MGs). Unfortunately, the brittleness of Mg-Zn MGs and poor glass forming ability (GFA) have hindered their further application. We have developed a composition series of completely new (not published) ternary Mg-Zn-Sr alloys with attractive properties in terms of possible future applications (density comparable to human bones, wide supercooled liquid region, low rate of degradability, etc.). These ternary alloys will serve as precursors for design of future highly alloyed systems with tuned mechanical properties and dissociation rate in human body.
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Nov 2020
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Karel
Saksl
,
Ildikó
Pethes
,
Pál
Jóvári
,
Zuzana
Molčanová
,
Juraj
Durisin
,
Beáta
Ballóková
,
László
Temleitner
,
Stefan
Michalik
,
Michaela
Sulikova
,
Katarína
Šuľová
,
Miloš
Fejercak
,
Dagmara
Varcholová
,
Rastislav
Motýľ
Abstract: Amorphous alloys consisting of elements present in the human body, such as magnesium, zinc and calcium, are currently extensively studied in order to utilize them as a material for biodegradable orthopaedic implants. amongst all Mg-Zn-Ca alloys investigated up to date, the Mg66Zn30Ca4 composition has the greatest potential for applications. Its critical casting thickness reaches a value of 5 mm, the compressive strength (716–854 MPa) is about 4 times the limit of human cortical bone while elastic modulus is (31 GPa) is only 3 times higher than that of human bone. During dissolution the alloy shows only marginal hydrogen evolution. Here we present a detailed, experiment-based structural investigation of Mg66Zn30Ca4. Structural and topological analysis of its atomic structure reveals a high number of predominantly icosahedral densely packed Zn-centred clusters. It is believed that the existence of these structural units is responsible for the suppression of internal diffusion and thus greatly improves glass formability.
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Apr 2021
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[17415]
Open Access
Abstract: Ferritin, a spherically shaped protein complex, is responsible for iron storage in bacteria, plants, animals, and humans. Various ferritin iron core compositions in organisms are associated with specific living requirements, health state, and different biochemical roles of ferritin isomers. Magnetoferritin, a synthetic ferritin derivative, serves as an artificial model system of unusual iron phase structures found in humans. We present the results of a complex structural study of magnetoferritins prepared by controlled in vitro synthesis. Using various complementary methods, it was observed that manipulation of the synthesis technology can improve the physicochemical parameters of the system, which is useful in applications. Thus, a higher synthesis temperature leads to an increase in magnetization due to the formation of the magnetite phase. An increase in the iron loading factor has a more pronounced impact on the protein shell structure in comparison with the pH of the aqueous medium. On the other hand, a higher loading factor at physiological temperature enhances the formation of an amorphous phase instead of magnetite crystallization. It was confirmed that the iron-overloading effect alone (observed during pathological events) cannot contribute to the formation of magnetite.
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Nov 2021
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